1. Field of the Invention
This invention relates to a method for the preparation of hydroxy-containing propylene carbonate insoluble butadiene polymer having an average molecular weight of about 400 to about 25,000 wherein the butadiene is polymerized in a homogeneous reaction medium composed of a propylene carbonate solution of aqueous hydrogen peroxide. More particularly, this invention is related to a simplified method for the preparation of hydroxy-containing butadiene polymers wherein butadiene is polymerized in a homogeneous reaction medium consisting essentially of a propylene carbonate solution of an aqueous solution of hydrogen peroxide to form a propylene carbonate insoluble hydroxy-containing butadiene polymer and wherein the reaction product is withdrawn from the reactor and allowed to settle, resulting in the formation of a supernatent layer of the insoluble butadiene polymer which is recovered with comparative ease.
2. Prior Art
It is known to prepare hydroxy-containing low molecular weight butadiene polymers by the hydrogen peroxide catalyzed polymerization of butadiene in a reaction medium. Such processes are disclosed, for example, in British Patent No. 957,788, Verdol et al. U.S. Pat. No. 3,796,762, Verdol et al. U.S. Pat. No. 3,808,281 and Burke et al. U.S. Pat. No. 3,673,168.
The Verdol et al. U.S. Patents disclose processes for polymerizing a conjugated diene monomer such as butadiene in the presence of aqueous hydrogen peroxide in an essentially water insoluble reaction medium such as an alicyclic, monocyclic alcohol or ketone (U.S. Pat. No. 3,796,762) or an essentially water-insoluble trihydrocarbol orthophosphate ester (U.S. Pat. No. 3,808,281).
The Verdol methods rely upon the use of water insoluble solvents so that the reaction system has at least two liquid phases.
The products that are formed by the Verdol et al. processes have molecular weights within the range of about 400 to about 25,000, contain at least about 1.8 predominantly allylic, terminal hydroxyl groups per average molecule and are prepared by the hydroperoxide catalyzed polymerization of the conjugated diene in the solvent, as above described, at a temperature of about 100.degree. to about 200.degree. C. in the presence of about 0.5 to about 30 wt. %, based on the conjugated diene monomer, of a hydrogen peroxide catalyst on an anhydrous basis, the hydrogen peroxide catalyst being used in the form of an aqueous solution containing from about 25 to about 75 wt. % of hydrogen peroxide.